1. Field of the Invention
The present invention relates to a method and an apparatus for providing a location based service in a wireless communication system. More particularly, the present invention relates to a method and an apparatus for providing a location-based service using a reference signal in an 802.16m system.
2. Description of the Related Art
Current mobile communication systems are advancing to provide the existing voice communication to various services, such as a multimedia broadcast, multimedia video, and multimedia message. Such a next-generation mobile communication system includes Institute of Electrical and Electronics Engineers (IEEE) 802.16e system recently commercialized, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) being standardized, IEEE 802.20 Ultra Mobile Broadband (UMB), and IEEE 802.16m system.
Recently, those next-generation mobile communication systems offer a Location Based Service (LBS) for providing various services based on a location of a mobile station.
Techniques for estimating the location of the mobile station can be classified into a network based technique and a mobile station based technique. The mobile station based technique includes a method for estimating the location of the mobile station using well-known Global Positioning System (GPS). The method using the GPS exhibits high accuracy of the location estimation, but its accuracy is low in a downtown area and it is inoperable indoors. The network based technique includes a method for estimating a location of a base station and a signal delay time between the mobile station and the base station, or an angle of arrival of the signal using a reference signal of the base station in the wireless communication network, and thus estimating the location of the mobile station. Disadvantageously, the method using the reference signal can raise the location estimation accuracy only when the Reference Signal (RS) is normally sent and received.
Meanwhile, the next-generation mobile communication system studies and develops a distributed base station architecture. The distributed base station architecture is constructed by separating Radio Frequency (RF) transceivers from the base station and relocating them near antennas so that the antennas can function with minimum loss of transmission power. That is, in the distributed base station architecture, a plurality of RF transceivers (hereafter, referred to as Remote Radio Heads or RF Remote Heads (RRHs)) is dispersed in one cell. The RRHs are installed at quite a distance from the base station and connected using optical fiber cables.
In the distributed base station architecture with the RRHs dispersed in one cell or in the wireless communication system based on a relay station, when the base station transmits the RS for the LBS, the RS is sent to the mobile station via the RRHs or the relay stations. However, when the RRHs or the relay stations transmit the RS for the LBS, the mobile station cannot distinguish which RRH or relay station transmits the received RS, and accordingly cannot accurately measure the distance between the base station and the mobile station.
Therefore, a need exists for a method for a mobile station to efficiently receive an RS and to determine which device sends the received RS.